Oral Contraceptive Use and Performance in Female Swimmers
by Becky Morgan, MD
Oral contraceptive agents (birth control pills) are often prescribed for the female athlete for contraceptive purposes, cycle regulation, or the treatment of dysmenorrhea (cramping and pain.) More recently, birth control pills have been prescribed in athletes with amenorrhea (absence of periods for more than 3 months) to avoid a decrease in bone density secondary to a lack of estrogen (the cause of skipped periods.) There are often concerns regarding performance in athletes prescribed these agents. The following is a brief summary of the action of birth control pills, and the potential complications and benefits of oral contraceptive use in swimmers.
The menstrual period is the result of a specific cycle of estrogen and progesterone secretion that occurs every 25-35 days (see diagram). The length of the cycle is variable among individuals and depends on many factors, such as physical or emotional stress, nutrition, and general health status. An alteration in any of the above factors may cause hormone levels to decrease and result in the interruption of the cycle that was previously normal for that individual. The end result may be an absence of menses, or irregular bleeding.
The effects of estrogen and progesterone on athletic performance during the different phases of the menstrual cycle are not clearly defined with current scientific information and may vary among individuals. Similarly, the effects of oral contraceptive agents (OCAs), on athletic performance are unclear. Current data reflects a wide variety of pills with differing dosages and different responses in individuals. In an effort to understand the potential positive and negative effects of OCAs on athletic performance, the components and function of the pill must be addressed.
Oral contraceptives are either a combination of estrogen and progesterone (the two female sex steroids), or progesterone alone. By supplying a steady level of these hormones in the blood, the pulse levels that stimulate ovulation are avoided. This prevents pregnancy, decreases the lining of the uterus and diminishes the amount of bleeding and cramping during the menstrual phase. The combination pill (estrogen plus progesterone) is the most commonly used formulation and will be the pill addressed in this discussion.
In addition to contraception, there are secondary advantages to OCAs. Regulation of the menstrual cycle, decreased premenstrual symptoms (bloating, fatigue, irritability, depression), decreased symptoms of dysmenorrhea (cramping and pain), and potential improvement in bone density are among those advantages.
Side effects of OCAs are highly variable among individuals. Fluid retention (and temporary weight gain), midcycle (break-through) bleeding, and adverse effects on hemostatic mechanisms (clotting factors and platelets) have all been described in the use of OCAs. The fear of significant weight gain has not been supported in the population studies done with newer low-dose combination pills. (There has been weight gain associated with the progesterone-only pill.)
Although understanding of the unique physiology of the female athlete has increased, there are still many questions to be answered with respect to metabolic, cardiopulmonary, and strength changes with OCAs. Currently, there is no significant difference seen in lactate levels in individuals taking birth control pills. There is conflicting data about changes in carbohydrate metabolism due to OCAs. Data demonstrate no significant change in oxygen consumption, cardiac index (a measure of the work efficiency of the heart), or strength in athletes on birth control pills.
The benefits of oral contraceptives, in addition to the prevention of pregnancy, may contribute significantly to athletic performance, but are difficult to quantify. Decreased cramping and pain may decrease time away from training. Decreased bleeding may prevent further depletion of iron stores and fatigue. Bone metabolism and density may improve with estrogen supplementation (in the form of birth control pills) in an athlete who has been amenorrheic.
Many questions remain in the evaluation of OCAs in athletic performance. Large controlled studies using similar pills are lacking. Additionally, there are many external influences, such as nutrition, emotional and physical stresses, and the use of other medications or supplements which may affect an individual’s response to birth control pills. Overall, the advantages of the pill seem to outweigh the potential risks. Female athletes should be counseled on the benefits and disadvantages in order to make an informed decision based on individual circumstances.
Much of the existing data regarding performance and OCAs involves older preparations with higher dose estrogen or various preparations of more recent pills. Newer studies involving larger populations and the same combination pill with longer follow-up are needed to provide more accurate information. There are many positive benefits of oral contraceptives that are difficult to quantify but may enhance training and competition. There is conflicting data regarding the role of estrogen replacement through OCAs in the maintenance of bone density in athletes.
Medals have been won, and World Records have been set by women in any phase of the menstrual cycle and by women taking oral contraceptives. There is great individual variation in response to oral contraceptives . The potential benefits very often outweigh the potential disadvantages. Each athlete needs to assess her individual circumstances when deciding to use oral contraceptives.
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Dr. Rebecca "Becky" Morgan is the team physician for the University of Tennessee Lady Vols. She is board certified in Family Practice and has a Certificate of Added Qualifications in Sports Medicine. Dr. Morgan received her Medical Doctorate from the University of South Alabama and completed her Family Practice Residency Training at the University of Alabama School of Medicine in Huntsville. She also served her Sports Medicine Fellowship at UASOM-Huntsville in 1996. Dr. Morgan completed a volunteer physician internship at the Olympic Training Center in Chula Vista, Calif., and also has experience with international competition through her work with the USA Swimming Program. She is a former member of the USA Swimming Sports Medicine/Science Committee and the USA Swimming Sports Medicine and Science Network.